The development of clause linkage in a second language has been studied extensively in the fields of applied linguistics and second language research. Several studies have focused on the development of specific types of complex structures, essentially based on the development of different classes of subordinate clauses distinguished by traditional grammar. The present contribution uses as a theoretical framework Role and Reference Grammar. RRG’s model of clause linkage proposes a different array of possible relations between combined clauses, adding the concept of cosubordination to the traditional dichotomy coordination/subordination, and pays attention to both predicate-based complexification within the clause and full clause combinations. RRG bases its classification of linkage types on the Interclausal Relations Hierarchy (Van Valin & LaPolla 1997), which unites syntactic and semantic aspects of clause complexification. The present article focuses on the syntax-semantics interface as realized within the Interclausal Relations Hierarchy, and on its impact on the acquisition of clause linkage structures by adolescent L2 learners of English. The corpus consists of oral narrative English interlanguage data elicited from 12- to 18-year-old Dutch-speaking secondary school pupils in Flanders (Belgium). Results show that RRG’s main principles of clause linkage are easily applicable to second language acquisition. The syntactic and semantic strength of a given juncture were found to often coincide in the data, as predicted, and any syntactic encoding of a semantic juncture which matches its semantic strength is likely to be acquired more easily and/or earlier than non-matching realizations. Although not all predictions made by RRG concerning structural variation were confirmed by the L2 English data, it is concluded that RRG provides a fruitful, coherent and powerful framework for studying clause linkage and sentence complexification in spoken L2 learner discourse.